1. Field of the Invention
The present invention relates to a gas adsorption filter that is provided at the breather hole for the pressure regulation of a semi airtight container that requires pressure regulation and has means for the elimination of chemical contaminants which enter through the breather hole.
2. Description of Related Art
Magnetic storage disk systems are extremely susceptible to chemical contamination. High molecular weight organic vapors are absorbed by the extremely smooth surfaces of the disk and the slider and, in addition, the characteristics of the fluid lubricants change. Other chemical contamination, for example, by SO2, causes the corrosion of the disk and head alloys and, especially, of magnetoresistive read-out elements. Previously, magnetic storage disk systems were made in a completely hermetically sealed form in order to prevent the entry of this kind of corrosive gas from outside. However, with the progressing changeover at the present time to stainless steel press molded plates for the top cover, the volume change distortion of completely hermetically sealed types due to temperature changes is great, producing problems such as head crashes, case deformation, and the like and it has become common to provide a breather hole so as to carry out pressure regulation. In addition, in order to prevent the entry of minute particles and the influx of corrosive gases, gas adsorption breather filters are often used that have a gas adsorbing agent and a particle filter combined in a single unit. With this filter, the entire breather hole is covered with an active carbon sheet or the like and the harmful gases that seek to enter are eliminated by passing the gases through the interior of the gas adsorbent material layer.
However, since air passes through the filter, nonwoven cloth type sheets, porous sheets, and the like having low permeability resistance are demanded. As a measure in response to that, schemes to reduce the permeability resistance such as decreasing the density and weight per unit area of the nonwoven cloth or increasing porosity have been employed. However, the resulting dilemma that is faced is that the packing density of the gas adsorbing agent is reduced and the adsorption effectiveness is lowered. Currently, in general, in contrast to breather filters that are not provided with a gas adsorbing agent, a tenfold pressure loss for gas adsorbent material sheets is common.
With the gas adsorption breather filter, a low pressure loss is demanded. In those cases where there is a high pressure loss, it is not possible for air to pass through to obtain satisfactory moderation with regard to the pressure changes in the magnetic storage disk system that accompany temperature changes when the system is turned on and off and with the high-speed rotation of the spindle motor. With this, air enters through those places where the sealing is weak rather than through the breather hole, bringing about an influx of contaminants. Because of this, an active carbon sheet such as an active carbon fiber woven fabric like Kynol is widely used for the gas adsorption breather filter. However, in the case of this woven fabric, the pressure loss is naturally low but the active carbon density per unit volume is low at 0.26 g/cc.
Incidentally, together with the currently increasing storage capacity of magnetic storage disk systems, their utilization environment is worsening due to a transition to higher rotation speeds and the spread of mobile type personal computer use and an increase in the amount of the activated carbon of the breather hole is desirable. In addition, because of the improvements that accompany higher hard disk drive (HDD) performance, the read heads of the HDD have come to be vulnerable with respect to contamination. Due to a transition to higher performance devices and use in environments other than a well-kept office environment, there has come to be a demand for not only the control of the influx of corrosive gases through the breather hole, but for much more stringent control of the gases and moisture generated by the motor and the like in the HDD. Because of this, there is always a demand that the amount of activated carbon that is enclosed in the filter be increased as much as possible.
However, when the amount of activated carbon is increased, the pressure loss for the filter increases and leakage problems such as those described before and the like are produced. Therefore, HDD manufacturers always are faced with the dilemma of the difficulty of achieving both the demanded reduction of filter pressure losses and the demanded increase in the amount of activated carbon at the same time.
A method has been proposed to resolve at one time the demand for an increase in the amount of activated carbon and the demand to reduce pressure losses as a method to resolve this dilemma (Japanese Laid-Open Patent Application Publication (Kokai) Number 2000-70649). With this, the contaminants are eliminated from the air that flows into a semi airtight container by having the air flow through the adsorbent material surface that is formed in the flow path and, since the air passes through a flow path having a low resistance, it is possible to keep the pressure loss low.
Incidentally, recently for HDDs, there has been an increasing demand for the rapid damping of pressure changes within the HDD, in other words, for breather filters with an extremely low resistance (pressure loss). The improvement of the damping performance of the breather filter is possible by relaxing the stringent specifications of the seal material. That is to say, if the pressure damping capability of the breather hole is satisfactorily increased even when the seal performance is low, the problem in which air flows other than through the breather hole does not occur. In addition, this makes it possible to relax the sealing specifications of not only the packing that fixes and seals the top cover but also the connector section for bringing in the electric power, inputting and outputting data and the like, as well as the portion for anchoring the motor and the like. By this means, it becomes permissible to use low-cost seal materials and, in addition, the simplification of the assembly process is possible. The result is that this makes a great contribution to reducing the total cost of the HDD.
In addition, the molding of the gas adsorbing agent as a protuberance which is formed in the space where the fluid that moves between the airtight container and the outside flows has been proposed as an improved plan (Japanese Laid-Open Patent Application Publication (Kokai) Number 2000-107543). This is done because the adsorbent material becomes a hindrance to the flow of the fluid and, as a result, the pressure drop is increased at the time of passing through the filter.
The methods that have been proposed here have as their aim solely the reduction of pressure losses by the filter and are proposed as measures to counteract that. However, two problems can be anticipated with these two methods.
(1) When the pressure loss becomes small, the air that is flowing through will quickly pass through the filter. In this case, the corrosive gases that are flowing through are not able to have satisfactory contact with the adsorbing agent and flow into the semi airtight container with a portion not adsorbed by the adsorbing agent. In other words, the corrosive gases that flow in without being captured adhere to the heads and media and there is a possibility that eventually the device will lapse into functional disorder. In other words, with these methods, the pressure loss is reduced but the measures they employ regarding gas adsorption performance are not satisfactory.
(2) These methods are effective in those cases where the influx of the air that flows through is from the center of the filter. However, in those cases where the breather hole is not in the center, in the same manner as in (1), as is to be expected, the air that flows through passes through the shortest distance and flows into the enclosure without being fully cleansed by the adsorbing agent.
These problems occur only in the space that is formed in which the air flows and are due to the fact that the direction and flow of the in flowing air are not controlled.
In general, an expansion of the air flow path and an enlargement of the opening section is demanded in order to reduce the pressure loss. However, in doing this, the harmful gases that flow into the HDD from outside cannot be fully absorbed, and the gas trapping capability is degraded to the degree that the pressure loss is reduced. As expected, the same kinds of problems as those described above are of concern.
These and other limitations are sought to be overcome by the present invention.
The present invention has as its benefit the provision of a gas adsorption filter that does not demand the modification of the HDD case, moreover, does not require plastic parts that lead to increased costs, and moreover, while having an adsorption ability that is equal to or better than filters of the past, is able to achieve an even lower pressure loss.
The present inventors, as a result of repeated diligent research aimed at solving the previously mentioned problems, arrived at the consummation of the present invention.
In accordance with the present invention, the gas adsorption filters shown herein are provided.
In one embodiment, there is provided a gas adsorption filter that is attached within a semi airtight container such that it covers the breather hole for regulating the pressure of said container and which has the function of capturing harmful gases that flow into said container passing through said breather hole. The gas adsorption filter is characterized in that said filter has an opening that is connected with and open to said breather hole and, moreover, comprises a base material having an attachment surface for attaching the filter to the inner wall of said container. A gas adsorption body is laminated and fixed to the gas flow path surface on the side opposite to that of said attachment surface of said base material, and on the gas contact surface on the side where said gas adsorption body is in contact with the gas flow path surface of said base material, there is at least one gas inflow orifice that is connected with and open to the opening of said base material. At least one gas discharge orifice is connected with an open to the outside of said gas adsorption body, and a groove section is formed that is connected with and open to said gas inflow orifice and said gas discharge orifice. Preferably, the groove width of said groove section is 10 mm or less, the proportion of the overall area of said groove section is 10 to 97%, and, in addition, the degree of nonuniform distribution of said groove section is xc2x170% or less.